Image forming apparatus having an improved power-mode switching function

ABSTRACT

An image forming device having a communication unit includes a system control unit which controls the entire image forming apparatus, the system control unit having a CPU that is set in one of a normal mode, a power-saving mode and a sleep mode by controlling a power supply unit. A real-time clock keeps track of hours, minutes and seconds of a current time and outputs a signal indicating the current time. A register stores a return time that indicates a time the CPU is to be switched from one of the power-saving mode and the sleep mode to the normal mode. A comparator compares the current time of the clock with the return time of the register, and outputs, when a match occurs, a control signal to the CPU so that the CPU is switched to the normal mode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Rule 1.53(b) continuation of U.S. Ser. No.10/107,919, filed Mar. 27, 2002 now U.S. Pat. No. 6,925,574, the entirecontents of which are herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image forming apparatus having acommunication function, such as a facsimile machine or a multi-functionmachine.

2. Description of the Related Art

Conventionally, there are various types of image forming device having acommunication function.

Japanese Laid-Open Patent Application No. 8-130595 discloses an imageforming device having a communication function, in which operationalhistory data is stored. Changes in the operational state of the imageforming device are stored as the operation history data. With this imageforming device, the user can detect whether the operational state hasbeen shifted to a power-saving mode, by accessing the changes in theoperational state in the stored operational history data. Suchconfiguration of the operational history data provides the user with thereliability of the image forming device.

Japanese Laid-Open Patent Application No. 9-307672 discloses an imageforming device having a communication function. In this image formingdevice, it is set in a power-saving mode at a suitable timing accordingto the operation situation and the facsimile receiving situation. A timeinterval between an end of the image forming operation or an end of thefacsimile receiving procedure and a start of automatic power-saving modesetting is controlled based on the operation history data and facsimilereceiving history data.

Japanese Laid-Open Patent Application No. 10-173840 discloses an imageforming device having a communication function. In this image formingdevice, a plurality of component units in which the supply/stop ofsource power to the component units is performed are grouped into a setof blocks. A power-saving unit is provided for each of such blocks. Atthe time of a start of power supplying, the power-saving unit for aspecific block is operated with a time delay, while the power-savingunits for other blocks are operated without delay. According to theconventional image forming device, it is possible to control the uselesspower consumption at the time of the power supplying start.

In recent years, many image forming devices are equipped with thelow-power setting function that reduces the power consumption in astandby state low as much as possible. For example, two conceivablemethods that attain the energy saving are as follows.

(1) The power source that supplies electric power to the electricalcomponents, such as a fixing heater and a drive motor, is turned off.

(2) The clock signal of the CPU is set at a low speed and a sleepcommand is issued to the CPU so that the CPU is set in the low-powerstate. Hereinafter, this state will be called the sleep mode.

However, in the conventional power-saving method, when there is astandby file, such as a time-specified transmission file thetransmission time of which is specified, the CPU at that time is notable to be switched to the sleep mode because it must perform thetransmission of the file at the specified time. Therefore, theconventional image forming device is capable of changing to the lowpower state only in the case of the above (1). When there is the standbyfile, the conventional image forming device has the problem in that thelarger the difference between the current time and the start time oftransmission specified by the standby file is, the larger the powerconsumption becomes.

Generally, the following files are stored in a facsimile system asinformation treated as the standby files.

(1) The time-specified transmission files with which the time of thetransmission is specified.

(2) The time-specified polling transmission standby files that arewaiting to be transmitted by the polling at the time specified therein.

(3) The retransmission files that are waiting to be retransmittedbecause of the occurrence of an error or during the conversation.

(4) The charging management reports with which the total of thecommunication charges is output and transmitted at a fixed time.

Conventionally, when the time-specified transmission files are stored,it has been impossible for the conventional image forming device toswitch the operating state of the CPU to the sleep mode because the CPUmust perform the transmission of such files at the specified time.Therefore, it is difficult that the conventional image forming deviceeffectively provide power saving when the time-specified transmissionfiles are stored.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved imageforming apparatus in which the above-described problems are eliminated.

Another object of the present invention is to provide an image formingapparatus having a communication function, which effectively providespower saving by setting the system control unit in a sleep mode evenwhen the time-specified transmission files are stored.

Another object of the present invention is to provide a control methodfor an image forming device having a communication function, whicheffectively provides power saving by setting the system control unit ina sleep mode even when the time-specified transmission files are stored.

The above-mentioned objects of the present invention are achieved by animage forming apparatus having a communication unit, comprising: a powersupply unit; a system control unit which controls the entire imageforming apparatus, the system control unit having a CPU that is set inone of a normal mode, a power-saving mode and a sleep mode bycontrolling the power supply unit; a real-time clock which keeps trackof hours, minutes and seconds of a current time and outputs a signalindicating the current time; a register which stores a return time thatindicates a time the CPU is to be switched from one of the power-savingmode and the sleep mode to the normal mode; and a comparator whichcompares the current time output from the clock with the return timestored in the register, and outputs, when a match occurs, a controlsignal to the CPU so that the CPU is switched to the normal mode.

The above-mentioned objects of the present invention are achieved by amethod of controlling an image forming apparatus having a communicationunit, the image forming apparatus including a power supply unit, asystem control unit controlling the entire image forming apparatus, thesystem control unit having a CPU that is set in one of a normal mode, apower-saving mode and a sleep mode by controlling the power supply unit,a real-time clock keeping track of hours, minutes and seconds of acurrent time and outputting a signal indicating the current time, aregister, and a comparator, the method comprising the steps of: settinga return time in the register, the return time indicating a time the CPUis to be switched from one of the power-saving mode and the sleep modeto the normal mode; causing the comparator to compare the current timeoutput from the clock with the return time stored in the register, andto output, when a match occurs, a control signal to the CPU; determiningwhether an error in the image forming apparatus is detected when animage formation is performed; switching the CPU from the normal mode tothe power-saving mode when it is determined that no error is detected;determining whether reduction of power supply to the system control unitby the power supply unit during the power-saving mode is possible;switching the CPU from the power-saving mode to the sleep mode when itis determined that the reduction is possible; and switching the CPU tothe normal mode when the comparator outputs the control signal to theCPU.

In the image forming apparatus of the present invention, the comparatoroutputs, when a match between the current time and the return timeoccurs, the control signal to the CPU so that the CPU is reset from oneof the power-saving mode and the sleep mode to the normal mode,irrespective of whether the time-specified transmission files arestored. It is possible that the image forming apparatus of the presentinvention reduces the power supply to the system control unit, and setthe system control unit in the sleep mode. Therefore, it is possiblethat the image forming apparatus of the present invention effectivelyprovide power-saving even when the time-specified transmission files arestored.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will beapparent from the following detailed description when read inconjunction with the accompanying drawings.

FIG. 1 is a block diagram of a facsimile apparatus to which oneembodiment of the image forming apparatus of the present invention isapplied.

FIG. 2 is a flowchart for explaining a power-mode switching processwhich is performed by a first preferred embodiment of the image formingapparatus of the present invention.

FIG. 3 is a flowchart for explaining a power-mode switching processwhich is performed by a second preferred embodiment of the image formingapparatus of the present invention.

FIG. 4 is a flowchart for explaining a power-mode switching processwhich is performed by a third preferred embodiment of the image formingapparatus of the present invention.

FIG. 5 is a flowchart for explaining a power-mode switching processwhich is performed by a fourth preferred embodiment of the image formingapparatus of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A description will now be provided of preferred embodiments of thepresent invention with reference to the accompanying drawings.

FIG. 1 shows the configuration of a facsimile system to which oneembodiment of the image forming apparatus of the present invention isapplied.

As shown in FIG. 1, the facsimile system generally includes an imagedata compression/decompression unit (DCR) 1, an image memory 2, a systemmemory 3 that stores system management data, an operation/display unit 4that has a liquid crystal display panel, an input key pad and so on, asystem control unit 5 that has a CPU 5 a controls the entire system, anda line buffer 6 that serves as a memory for data transmission. Thefacsimile system further includes an image reader unit 7 that opticallyreads an image, an automatic document feeder (ADF) 7 a that includes adocument width sensor and automatically conveys a document to the imagereader unit 7, a recording/printing unit 8 that records image data on arecording sheet by using an electro-photographic printing process, asheet supply unit 8 a which conveys a recording sheet to therecording/printing unit 8, and a real time clock (RTC) 9 that keepstrack of hours, minutes and seconds of the current time and makes thisdata available to the CPU 5 a.

The facsimile system further includes a communication control unit (CCU)10, a modem 10 a which has analog-to-digital and digital-to-analogconversion functions and various tone output and detection functions, anetwork control unit (NCU) 11, a power supply unit 12 that supplieselectric power to the electrical components constituting the facsimilesystem, a heater 12 a that is provided in a fixing unit of therecording/printing unit 8, a thermistor 13 that detects a temperature ofthe fixing unit, and a printer unit 14 that is provided as an optionalequipment.

The power supply unit 12 is controlled by the system control unit 5. Thepower supply locations and the source power voltages are determinedbased on the power management information stored in the system memory 3.For example, the power supply unit 12 is provided such that the outputpower voltages of +5V, +24V and −12V are produced from AC 100V, and aheater control signal is supplied to switch ON/OFF the heater 12 a, andthe fixing unit is heated by the heater 12 a such that it is maintainedat a fixed temperature.

The system control unit 5 is equipped with a power-mode switchingfunction to set the CPU 5 a in one of the normal mode, the power-savingmode, and the sleep mode. The system control unit 5 includes a ROM(read-only memory) and a RAM (random access memory) in addition to theCPU 5 a. The power-mode switching function is achieved by using asoftware (program) stored in the ROM and loaded to the RAM. When the CPU5 a is set in the normal mode, the supply of the output power to theelectrical components, including the heater 12 a, by the power supplyunit 12 is turned ON and the facsimile system is placed in a standbystate to perform the printing of the image data. When the CPU 5 a is setin the power-saving mode, the supply of the output power to thecomponents, which do not always need to receive the power supply, by thepower supply unit 12, is cut off, and the facsimile system is placed ina standby state.

Furthermore, when the CPU 5 a is set in the power-saving mode, thesupply of the output power to the electrical components, including theheater 12 a, by the power supply unit 12 is cut off, or the output powersupplied to the electrical components is reduced. On the other hand,when the CPU 5 a is set in the sleep mode, the supply of the outputpower to the CPU 5 a by the power supply unit 12 is cut off and only theclock signal from the CPU 5 a is actively supplied to the respectivecomponents of the facsimile system.

In the image forming apparatus of the present embodiment, the powerconsumption when the CPU 5 a is set in one of the normal mode, thepower-saving mode and the sleep mode is predetermined so as to satisfythe conditions that the power consumption in the sleep mode is smallerthan that in the power-saving mode; and the power consumption in thepower-saving mode is smaller than that in the normal mode.

In the image forming apparatus of the present embodiment, the RTC 9includes a clock part 9 a, a setting register 9 b and a comparator 9 c.The clock part 9 a outputs a signal indicating the current time. Thesetting register 9 b stores a return time indicating a time the CPU 5 ais to be switched from one of the power-saving mode and the sleep modeto the normal mode. The comparator 9 c compares the current time outputfrom the clock part 9 a with the return time output from the register 9b, and outputs, when a match between the current time and the returntime occurs, an interrupt signal to the CPU 5 a so that the setting ofthe CPU 5 a in one of the power-saving mode and the sleep mode iscanceled and the CPU 5 a is switched to the normal mode.

The setting of the return time in the register 9 b is performed in thefollowing manner. When there is an input of the return time settingcommand from the operation/display unit 4, the return time is stored inthe system memory 3. The system control unit 5 sets the return time,read from the system memory 3, in the register 9 b of the RTC 9 whensetting the CPU 5 a in the sleep mode or the power-saving mode.

The switching control of the system control unit 5 to switch the normalmode to the power-saving mode is caused when one of the following eventsoccurs: (1) there is an input of the power-saving mode setting commandfrom the operation/display unit 4; (2) the duration of time in which thenormal mode of the CPU 5 a is continuously held exceeds a predeterminedtime. This predetermined time, which specifies the time the CPU 5 a isto be switched from the normal mode to the power-saving mode, is storedin the system memory 3 by inputting a time setting data from theoperation/display unit 4. Moreover, the switching control of the systemcontrol unit 5 to return or switch the CPU 5 a from the power-savingmode to the normal mode is caused when one of the following eventsoccurs: (1) there is an input of the normal mode returning command fromthe operation/display unit 4; (2) there is a facsimile reception datareceived from the communication line and stored in the image memory 2;(3) an original document is placed onto the ADF 7 a.

The switching control of the system control unit 5 to switch the CPU 5 ato the sleep mode after the power supply to the electrical components isturned off is caused when it is determined that no error in thefacsimile system is detected by the CPU 5 a and that a temperature ofthe fixing unit in the recording/printing unit 8 of the facsimilesystem, detected by the thermistor 13, is below a predeterminedtemperature. The setting of the CPU 5 a in the sleep mode is canceledwhen one of the following events occurs: (1) there is the control signaloutput from comparator 9 c to the CPU 5 a; (2) there is an input of thesleep mode cancel command from the operation/display unit 4; (3) thereis a facsimile reception data received from the communication line andstored in the image memory 2; (4) an original document is placed ontothe ADF 7 a. When the CPU 5 a is returned to the normal mode, the powersupply to the CPU 5 a is turned on in the same manner as that of theusually supplied to the CPU 5 a.

FIG. 2 shows a power-mode switching process which is performed by afirst preferred embodiment of the image forming apparatus of the presentinvention.

When the image formation is performed by the image forming apparatus,the CPU 5 a is switched to the normal mode. The supply of the outputpower to the electrical components, including the heater 12 a of thefixing unit of the recording/printing unit 8, by the power supply unit12 is turned on, and the fixing unit is heated to an operationaltemperature so that the image formation is performed by using therecording/printing unit 8. After the image formation is performed, theCPU 5 a is usually set in the normal mode.

As shown in FIG. 2, at a start of the power-mode switching process, thesystem control unit 5 determines whether there is an input of thepower-saving mode setting command from the operation/display unit 4(S1). When the result at the step S1 is affirmative, the control of thesystem control unit 5 is transferred to the next step S3. When theresult at the step S1 is negative, the system control unit 5 determineswhether the duration of time in which the normal mode of the CPU 5 a iscontinuously held exceeds the predetermined time (which is called theautomatic shift time) (S2). As described above, when the automatic shifttime is reached, the CPU 5 a is automatically shifted to thepower-saving mode. When the result at the step S2 is negative, thecontrol of the system control unit 5 is returned to the step S1. Whenthe result at the step S2 is affirmative, the control of the systemcontrol unit 5 is transferred to the next step S3.

In the step S3, the system control unit 5 determines whether no error inthe facsimile system is detected by the CPU 5 a. Namely, it is checkedin the step S3 if the switching control of the system control unit toswitch the CPU 5 a to the power-saving mode is possible. When the resultat the step S3 is negative (an error is detected), it is determined thatthe switching control is not possible, and the control of the CPU 5 a isreturned to the above step S1. When the result at the step S3 isaffirmative (no error), it is determined that the switching control ispossible. In this case, the system control unit 5 controls the powersupply unit 12 so that the supply of the output power to the electricalcomponents by the power control unit 12 is cut off (S4). In the step S4,the system control unit 5 switches the CPU 5 a from the normal mode tothe power-saving mode.

For example, in the facsimile system, it is determined whether there isa facsimile reception data received from the communication line andstored in the image memory 2. When there is no facsimile reception dataand no error is detected, the system control unit 5 switches the CPU 5 afrom the normal mode to the power-saving mode. In the power-saving mode,the supply of the output power +24V to the image reader unit 7 and therecording/printing unit 8 by the power supply unit 8 is cut off.Consequently, it is possible to prevent the power consumption caused bythe leaking current in the electrical components.

After the step S4 is performed, the system control unit 5 determineswhether the return time, which indicates the time the CPU 5 a is to beswitched to the normal mode, is set in the system memory 3 (S5). Whenthe result at the step S5 is negative, the control of the system controlunit 5 is transferred to the next step S7. When the result at the stepS5 is affirmative, the system control unit 5 sets the return time intothe register 9 b of the RTC 9.

After the step S6 is performed or when the result at the step S5 isnegative, the system control unit 5 sends a sleep mode setting commandto the CPU 5 a (S7). After the step S7 is performed, the system controlunit 5 switches the CPU 5 a from the power-saving mode to the sleep mode(S8).

In the sleep mode, the system control unit 5 causes the comparator 9 cof the RTC 9 to compare the current time output from the clock part 9 awith the return time output from the setting register 9 b (S9). Afterthe step S9 is performed, the system control unit 5 determines whetherthere is a match between the current time and the return time, based onthe control signal (the interrupt signal) output by the comparator 9 c(S10). When the result at the step S10 is negative, the control of thesystem control unit 5 is returned to the step S10. When a match occurs(the return time is reached), the system control unit 5 cancels thesetting of the CPU 5 a in the sleep mode in accordance with the controlsignal output to the CPU 5 a (S11). When the setting of the CPU 5 a inthe sleep mode, the CPU 5 a is usually switched to the power-savingmode. After the step S11 is performed, the system control unit 5switches the CPU 5 a from the power-saving mode to the normal mode byperforming the switching control (S12).

In a case where the return time is reached after the power supply to theelectrical components is turned off and before the CPU 5 a is switchedto the sleep mode, the interrupt signal output from the comparator 9 cis supplied to the CPU 5 a. In this case, the CPU 5 a is switched to thenormal mode. Moreover, when the return time is not set in the systemmemory 3, the event that the control signal output by the comparator 9 cis sent to the CPU 5 a does not take place. In such a case, the normalmode setting command is manually inputted by using the operation/displayunit 4 in order to switch the CPU 5 s to the normal mode.

Next, an operation of the image forming apparatus in the sleep mode willbe explained:

Before switching the CPU 5 a to the sleep mode and after the powersupply to the electrical components by the power supply unit 8 is cutoff, the system control unit 5 determines whether there is no error(such as, paper jam or lack of recording sheet) in the image formingapparatus is detected by the CPU 5 a. When an error is detected, thesystem control unit 5 inhibits the setting of the CPU 5 a in the sleepmode. In this case, the system control unit 5 sends an error message tothe operation/display unit 4 so that the error message is displayed onthe display unit 4 in a visible manner.

Furthermore, the system control unit 5 determines whether a temperatureof the fixing unit in the recording/printing unit 8, detected by thethermistor 13, is below the predetermined temperature. The systemcontrol unit 5 inhibits the setting of the CPU 5 a in the sleep modewhen it is determined that the detected temperature is not below thepredetermined temperature. Only when it is determined that the detectedtemperature is below the predetermined temperature, the system controlunit 5 switches the CPU 5 a to the sleep mode. In addition, when theerror in the facsimile system is eliminated, the system control unit 5switches the CPU 5 a to the sleep mode based on the detected temperatureof the fixing unit.

Moreover, when the facsimile reception is carried out during the sleepmode, the CCU 10 outputs an interrupt signal to the CPU 5 a. The settingof the CPU 5 a in the sleep mode is canceled in response to theinterrupt signal output from the CCU 10. After the setting of the CPU 5a in the sleep mode is canceled, the memory reception is performed andthe received image data is stored in the image memory 2. After thememory reception is performed, the CPU 5 a is switched to the sleep modeby performing the control procedure of the steps S1 through S12 in FIG.2.

When a large amount of image data is transmitted to the facsimile systemand the image memory 2 stores the image data to the full capacity, thefacsimile reception beyond the full capacity of the image memory 2 isimpossible. Therefore, when the remaining capacity of the image memory 2is below a predetermined quantity, the sleep mode is usually switched tothe normal mode, and the heater 12 a is heated, the printing of all theimage data in the image memory 2 is carried out, so that the imagememory 2 is changed into an empty state.

Then, when the return time is reached and the CPU 5 a usually returns tothe normal mode, the printing of the image data stored in the imagememory 2 is carried out.

In the above-described embodiment, the setting register 9 b is providedinside the RTC 9, and using the clock function of the RTC 9 and thesetting time of the register 9 b, it is possible that the CPU 5 a is setin the sleep mode even when the time-specified transmission files arestored. The switching control of the system control unit 5 to return theCPU 5 a to the normal mode from the power-saving mode inclusive of thesleep mode can be performed at the specified time.

FIG. 3 shows a power-mode switching process which is performed by asecond preferred embodiment of the image forming apparatus of thepresent invention.

In the second preferred embodiment, it is possible for the image formingapparatus to switch the CPU 5 a to the sleep mode before startingtime-specified operations related to various kinds of facsimiletransmission and reception, in addition to the return function to thenormal mode from the power-saving mode at the specified time as in thefirst preferred embodiment.

Generally, the following files are stored in the facsimile system asinformation treated as the standby files.

(1) The time-specified transmission files with which the time of thetransmission is specified.

(2) The time-specified polling transmission standby files which arewaiting to be transmitted by the polling at the time specified therein.

(3) The retransmission files which are waiting to be retransmittedbecause of the occurrence of an error or during the conversation.

(4) The charging management reports with which the total of thecommunication charges is output and transmitted at a fixed time.

It is supposed that, when the necessity occurs, the specified time andthe specified operations which perform the transmission of the abovefiles are, in advance, inputted into the system memory 3 by using theoperation/display unit 4.

As shown in FIG. 3, at a start of the power-mode switching process, thesystem control unit 5 determines whether the time-specified transmissionoperations (the standby files) are set in the system memory 3 (S21).When the result at the step S21 is affirmative, the system control unit5 reads from the system memory 3 the time-specified transmissionoperation with the earliest transmission time (S22). The system controlunit 5 sets the earliest transmission time of the time-specifiedtransmission operation into the setting register 9 b of the RTC 9 as thereturn time (S23).

When the result at the step S21 is negative, the system control unit 5sets the return time into the setting register 9 b. After this operationor the step S23 is performed, the system control unit 5 performs thecontrol procedure of the steps S1 through S12 in FIG. 2 in order to setthe CPU 5 a in the power-saving mode or the sleep mode, if necessary,and effectively provide power saving of the facsimile system. Then, thepower-mode switching process is performed, and the CPU 5 a is set to thesleep mode. When the return time is reached, the sleep mode is usuallyreturned to the normal mode.

Next, the time-specified transmission is explained as an example of thepower-mode switching process shown in FIG. 3.

By using the operation/display unit 4, the time-specified transmissionoperation is chosen, and the original document is placed on the ADF 7 a.Furthermore, the destination address and the transmission start time areinputted from the operation/display unit 4, and then the start key ispressed. The image of the document on the ADF 7 a is optically read bythe image reader unit 7, and the image data from the image reader unit 7is sent to the line buffer 6. The image data sent to the line buffer 6is compressed by the DCR 1. The compressed image data is stored in theimage memory 2 as the standby file. On the other hand, the inputdestination address, the input transmission start time, and the storagelocation data of the standby file are set in the system memory 3.

When there is an input of the power-saving mode setting command from theoperation/display unit 4, or when the continuation period of the normalmode exceeds a predetermined period, the CPU 5 a is switched to thepower-saving mode. The power supply to the electrical components by thepower supply unit 4 is cut off. The CPU 5 a is continuously set in thepower-saving mode until the specified time is reached. After thespecified time is reached, the CPU 5 a is switched from the power-savingmode to the sleep mode. The system control unit 5 reads the transmissionstart time from the system memory 3 at a fixed interval and compares theread time with the current time of the RTC 9. When a match occurs, thecomparator 9 c outputs the interrupt signal to the CPU 5 a so that thesetting of the CPU 5 a in the sleep mode is canceled. The CPU 5 a isusually returned from the sleep state to the normal mode. The facsimilesystem is set in the normal mode, and the transmission of the standbyfile to the destination address is performed at the specified time.

When the time-specified transmission files as shown in the above items(1) through (4) are stored, the power supply to the electricalcomponents by the power supply unit cannot be turned OFF in theconventional image forming device, and the CPU cannot be switched to thesleep mode in such cases. However, in the image forming apparatus of thepresent embodiment, even when the standby file is stored, the time ofthe earliest transmission operation is read from the time-specifiedtransmission operations in the system memory 3, and the transmissionstart time is set to the register 9 b of the RTC 9 as the return timebefore shifting to the sleep mode. When the return time is reached, thereturning to the normal mode is also attained.

In addition, the manual operation using the display/operation unit 4 isperformed (or in accordance with the elapsed time), and the switching ofthe CPU 5 a to the power-saving mode after the automatic returningfunction is performed.

FIG. 4 shows a power-mode switching process which is performed by athird preferred embodiment of the image forming apparatus of the presentinvention.

In the present embodiment, the image forming apparatus is equipped withnot only the function of the first preferred embodiment to switch theCPU 5 a from the normal mode to the power-saving mode, but also thefunction to automatically switch the CPU 5 a from the power-saving modeto the normal mode at the specified time.

Usually, the setting data including the return time and the shift timeis inputted from the operation/display unit 4, and the setting data isstored in the system memory 3. A plurality of sets of the shift/returntimes for one day may be registered. Alternatively, it is possible toregister the shift/return time for one week.

A description will be given of the power-mode switching process in thesecond preferred embodiment with reference to FIG. 4.

As shown in FIG. 4, at a start of the power-mode switching process, thesystem control unit 5 causes the system memory 3 to store the shift timethat is used to switch the CPU 5 a from the normal mode to thepower-saving mode (S31). The system control unit 5 causes the systemmemory 3 to store the return time that is used to return the CPU 5 a tothe normal mode (S32).

After the step S32 is performed, the system control unit 5 compares thecurrent time of the RTC 9 with the shift time stored in the systemmemory 3 (S33). The system control unit 5 determines whether a matchbetween the current time and the shift time occurs (S34). When theresult at the step S34 is affirmative, the control of the system controlunit 5 is transferred to the next step S35. Otherwise the step S33 isrepeated.

After the shift time is reached (YES of S34), the system control unit 5sets the registered return time into the setting register 9 b of the RTC9 (S35). After the step S35 is performed, the system control unit 5performs the control procedure of the steps S1-S12 shown in FIG. 2.Then, the power-mode switching process is performed, and the CPU 5 a isset to the sleep mode. When the return time is reached, the setting ofthe CPU 5 a in the sleep mode is canceled and the CPU 5 a is usuallyreturned to the normal mode.

Next, the case where one set of the shift time and the return time forone day is registered will now be described. Since the facsimile systemis frequently used from 9:00 to 17:00 in the day, the CPU 5 a is notswitched to the power-saving mode during this period. However, in thenight after 17:00 or in the early morning before 9:00, the facsimilesystem is not frequently used, and during this period, the CPU 5 a isswitched to the power-saving mode. In the above-mentioned case, thesetting data including the return time 9:00 and the shift time 17:00 isregistered in the system memory 3.

Next, if the shift time and the return time are registered, the systemcontrol unit 5 reads the registered time from the system memory 3 andcompares it with the current time from the clock 9 a of the RTC 9. Whena match between the shift time and the current time occurs, the returntime is set to the setting register 9 b of the RTC 9, and the outputsignal of the setting register 9 b causes the CPU 5 a to be set in thesleep mode. And, when the return time is reached, the setting of the CPU5 a in the sleep mode is canceled and the CPU 5 a is returned to thenormal mode.

In the third preferred embodiment, the setting data (the return time) toswitch the power-saving mode to the normal mode and the setting data(the shift time) to set the CPU 5 a in the power-saving mode areregistered in the system memory 3. It is possible to perform thepower-mode switching process in accordance with the purpose of the usethereof.

FIG. 5 shows a power-mode switching process which is performed by afourth preferred embodiment of the image forming apparatus of thepresent invention.

In the second preferred embodiment, when there are the standby files,the execution start time of each file is set up as the return time fromthe power-saving mode to the normal mode. However, the switching betweenthe power-saving mode and the normal mode may be repeated for a shorttime. For example, when a broadcasting transmission file having tendestination locations is stored as the standby file in the facsimilesystem, the transmission to the second destination is started about 12seconds after the end of the transmission to the first destination.Namely, when the transmission of the file to the first destination iscomplete, the CPU 5 a is switched to the power-saving mode. After 12seconds from that timing, the CPU 5 a is returned from the power-savingmode to the normal mode, and the transmission of the same file to thesecond destination is performed.

In this case, the relay switching sound may frequently occur when thesupply of the output power to the electrical components by the powersupply unit 12 is turned off. Moreover, when the setting of thepower-saving mode is just performed at the return time, the automaticreturn function may not be properly performed.

The power-mode switching process of the fourth preferred embodiment isprovided in order to eliminate the above-mentioned problem. In thepresent embodiment, the normal mode is kept without being switched tothe power-saving mode, when a time interval between the current time andthe return time is smaller than a predetermined interval.

As shown in FIG. 5, the system control unit 5 determines whethertime-specified transmission operations are stored in the system memory 3(S41). When the result at the step S41 is affirmative, the systemcontrol unit 5 reads from the system memory 3 the time-specifiedtransmission operation with the earliest transmission time (S42). Thesystem control unit 5 sets the earliest transmission time of thetime-specified transmission operation into the setting register 9 b ofthe RTC 9 as the return time (S43).

When the result at the step S41 is negative, the system control unit 5sets the return time into the setting register 9 b. After this operationor the step S43 is performed, the system control unit 5 calculates adifference between the current time of the clock 9 a and the return timeof the setting register 9 b (S44). After the step S44 is performed, thesystem control unit 5 determines whether the calculated time differenceis larger than a given period (S45).

When the result at the step S45 is affirmative, the system control unit5 performs the control procedure of the steps S1 through S12 in FIG. 2in order to set the CPU 5 a in the power-saving mode or the sleep mode,if necessary, and effectively provide power saving of the facsimilesystem. On the other hand, when the result at the step S45 is negative,the system control unit 5 inhibits the setting of the CPU 5 a in thepower-saving mode (S46). After the step S46 is performed, the systemcontrol unit 5 performs the control procedure of the steps S1 throughS12 in FIG. 2. Then, the power-mode switching process is performed, andthe CPU 5 a is set to the sleep mode. When the return time is reached,the sleep mode is usually returned to the normal mode.

Accordingly, in the present embodiment, the normal mode is kept withoutbeing switched to the power-saving mode, when the time differencebetween the current time and the return time is smaller than the givenperiod. It is possible to eliminate the problems, such as the frequentoccurrence of the relay switching sound or the improper performance ofthe automatic return function, which may arise if the switching betweenthe normal mode and the power-saving mode is performed for a short time.

In the above-described embodiments, when the return time is reachedafter the CPU 5 a is set in the power-saving mode or the sleep mode, theCPU 5 a is returned to the normal mode. At this time, the supply of theoutput power to the heater 12 a by the power supply unit 12 is turned ONas soon as the CPU 5 a is set in the normal mode.

Therefore, when the memory reception occurs, or when performing thefacsimile reception according to the return time, the printing of theimage data onto paper can be immediately started. However, in the caseof the facsimile system, the starting of the printing at the return timewhen the CPU 5 s is returned to the normal mode is not required becausethe memory reception does not always occur, and depending on the useenvironment there is the case where it is unnecessary to immediatelyperform the printing of the image data.

By taking the above-mentioned matter into consideration, the normal modereturning function in the above embodiments may be modified in such amanner that, when the setting of the CPU 5 a in the sleep mode iscanceled, the CPU 5 a is returned to the power-saving mode, rather thanto the normal mode. By storing both the original setting data to performthe normal mode returning function and the modified setting data toattain the modified function into the system memory 3, the operation mayselect one of the original setting data and the modified setting data inorder to perform the selected function according to the user demands ofthe image forming apparatus.

In the image forming apparatus of the above-described embodiment, thepower consumption when the CPU 5 a is set in one of the normal mode, thepower-saving mode and the sleep mode is predetermined so as to satisfythe conditions that the power consumption in the sleep mode is smallerthan that in the power-saving mode, and the power consumption in thepower-saving mode is smaller than that in the normal mode (normalmode>power-saving mode>sleep mode).

By configuring the image forming apparatus in the above-mentionedmanner, the setting of the CPU 5 a in the sleep mode may be determinedbased on the setting data of the system memory 3. For example, the sleepmode of the CPU 5 a is canceled when the input of the sleep mode cancelcommand from the operation/display unit 4 occurs, or when the receptionof image data from the communication line occurs, or when the outputsignal from the comparator 9 c of the RTC 9 occurs. Moreover, when thesetting of the CPU 5 a in the sleep mode is canceled, the controloperation to return the CPU 5 a to either the power-saving mode or thenormal mode may be performed based on the setting data of the systemmemory 3.

Moreover, the modification may be made such that the presence of thereceived image data in the image memory 2 is detected, and one of theoriginal setting data and the modified setting data in the system memory3 is selected as the result of the detection of the image data in theimage memory 2. When there is the image data in the image memory 2, theCPU 5 a is switched to the normal mode and the printing of the imagedata on paper is performed. When there is no image data in the imagememory 2, the supply of the output power to the heater 12 a by the powersupply unit 12 is turned off, and the sleep mode of the CPU 5 a isreturned to the power-saving mode.

Furthermore, when the return time is reached, the normal mode returningfunction is performed in each of the above-described embodiments. Forthis reason, in order to heat the fixing unit by the heater 12 a and setthe facsimile system in the standby state to perform the printing of theimage data, the time the facsimile system is set in the standby statebecomes later than the specified return time. It is possible to make thespecified return time that is set in the setting register 9 b slightlysmaller than the time as originally specified, such that the time thefacsimile system is set in the standby state is in conformity with thereturn time.

Moreover, in the above-described embodiments, the present invention isapplied to the facsimile system as an example. However, the presentinvention is applicable also to a multi-function machine which hasvarious image forming functions including the copying, the printing andthe facsimile functions. When the present invention is applied to themulti-function machine, the conditions of the multi-function machine inwhich it is returned to the usual mode after the return time is reachedshould be determined in detail depending on which function of thevarious image forming functions is mainly used.

The multi-function machine is equipped with function selecting keys. Itis possible to configure the multi-function machine such that, when oneof these keys is pressed, the operator is automatically requested tochange the contents of the system memory 3 in accordance with, thedesired setting data. For example, when the copying function selectingkey is pressed, the contents of the system memory 3 are changed so thatthe temperature of the fixing unit is raised to a high temperature atwhich the printing of the image data is possible after the power-savingmode is switched to the normal mode. When the printing functionselecting key is pressed, the contents of the system memory 3 arechanged so that the fixing unit is set in a preheating state and thetemperature of the fixing unit is set at a temperature lower than thehigh temperature at which the printing of the image data is possibleafter the power-saving mode is switched to the normal mode. When thefacsimile function selecting key is pressed, the contents of the systemmemory 3 are changed so that the power supply to the heater of thefixing unit is cut off after the power-saving mode is switched to thenormal mode. Further, it is possible that the contents of the systemmemory 3 may be changed when the input setting data from theoperation/display unit 4 occurs, such that they are suited to the useenvironment of the image forming apparatus.

The present invention is not limited to the above-described embodiments,and variations and modifications may be made without departing from thescope of the present invention. For example, although the image datawith which the facsimile reception is performed through thecommunication line is recorded in the above-described embodiments, theimage data that is received by using the e-mail function may be recordedby the image forming apparatus. Furthermore, the image data may be inputfrom an external terminal to the image forming apparatus by using thecommunication line or via a local area network (LAN).

Further, the present invention is based on Japanese priority applicationNo. 2001-95063, filed on Mar. 29, 2001, the entire contents of which arehereby incorporated by reference.

1. An electrical device having a communication unit, the electricaldevice comprising: a system control unit controlling the entireelectrical device, the system control unit having a CPU that is set inone of a normal mode and a power-saving mode by controlling a powersupply unit, wherein, when the CPU is set in the normal mode, a poweroutput from the power supply unit is supplied to electrical componentsof the electrical device, and when the CPU is set in the power-savingmode, the power supplied to the electrical components in the normal modeis cut off or reduced and the electrical device is set in a standbystate; a real-time clock keeping track of hours, minutes and seconds ofa current time and outputting a signal indicating the current time; aregister storing at least a return time that indicates a time the CPU isto be switched from the power-saving mode to the normal mode; acomparator comparing the current time output from the clock with thereturn time stored in the register, and outputting, when a match occurs,a control signal to the CPU so that the CPU is automatically switchedfrom the power-saving mode to the normal mode; and a system memory whichstores at least one time-specified operation data; wherein the systemcontrol unit comprises: a reading unit reading, when the time-specifiedtransmission operation data is stored in the system memory, atime-specified operation with an earliest transmission time from thesystem memory; and a setting unit setting the earliest transmissiontime, read by the reading unit, into the register as the return time. 2.The electrical device according to claim 1 wherein the system controlunit is configured so that the CPU is set in one of the normal mode, thepower-saving mode, and a sleep mode by controlling the power supplyunit, and, when the CPU is set in the sleep mode, a power consumption inthe sleep mode is made to be smaller than a power consumption in thepower-saving mode, the system control unit cancels the setting of theCPU is the sleep mode based on the control signal output by thecomparator when the match occurs.
 3. The electrical device according toclaim 2 wherein, when an error in the electrical device is detectedbefore switching the CPU from the normal mode to the power-saving mode,the system control unit inhibits the setting of the CPU in thepower-saving mode.
 4. The electrical device according to claim 2wherein, after the CPU is set in the power-saving mode, the systemcontrol unit sets the return time into the register immediately beforesetting the CPU in the sleep mode.
 5. The electrical device according toclaim 4 wherein, after the CPU is set in the power-saving mode, thesystem control unit sets the return time in the sleep mode when atemperature of an internal component of the electrical device is below apredetermined temperature.
 6. The electrical device according to claim 1further comprising an image memory which stores image data received froman external device through the communication unit, wherein the systemcontrol unit performs a facsimile reception by using the image memory.7. The electrical device according to claims 6 further comprising aprinting unit which prints image data on paper, wherein, when the CPU isset in the power-saving mode and an amount of the image data stored inthe image memory exceeds a predetermined amount, the system control unitswitches the CPU from the power-saving mode to the normal mode andcauses the printing unit to print the image data, read from the imagememory, on paper so that the amount of the image data stored in theimage memory is reduced.
 8. The electrical device according to claim 1wherein the system control unit stores in the system memory a shift timethat indicates a time the CPU is to be switched from the normal mode tothe power-saving mode, the system control unit storing in the systemmemory the return time that indicates the time the CPU is to be switchedto the normal mode, and the system control unit switching the CPU to thepower-saving mode when the shift time is reached, and switching the CPUto the normal mode by causing the register to output the control signalto the CPU when the return time is reached.
 9. The electrical deviceaccording to claim 1 wherein the system control unit further comprises acalculating unit calculating a difference between the current time ofthe clock and the return time of the register, and wherein the systemcontrol unit inhibits the setting of the CPU in the power-saving modewhen the time difference calculated by the calculating unit is notlarger than a given period.
 10. An electrical device having acommunication unit, the electrical device comprising: a system controlunit controlling the entire electrical device, the system control unithaving a CPU that is set in one of a normal mode and a power-saving modeby controlling a power supply unit, wherein, when the CPU is set in thenormal mode, a power output from the power supply unit is supplied toelectrical components of the electrical device, and when the CPU is setin the power-saving mode, the power supplied to the electricalcomponents in the normal mode is cut off or reduced and the electricaldevice is set in a standby state; a real-time clock keeping track ofhours, minutes and seconds of a current time and outputting a signalindicating the current time; a register storing at least a return timethat indicates a time the CPU is to be switched from the power-savingmode to the normal mode; a comparator comparing the current time outputfrom the clock with the return time stored in the register, andoutputting, when a match occurs, a control signal to the CPU so that theCPU is automatically switched from the power-saving mode to the normalmode; and a system memory which stores at least one time-specifiedoperation data; wherein the system control unit comprises: a readingunit reading, when the time-specified transmission operation data isstored in the system memory, a time-specified operation with an earliesttransmission time from the system memory; and a setting unit setting theearliest transmission time, read by the reading unit, into the registeras the return time, wherein the system control unit sets into theregister a second return time having a value smaller than a value of thereturn time originally specified, so that the CPU is switched to thenormal mode completely when the originally specified return time isreached.
 11. The electrical device according to claim 10, wherein thesystem control unit is configured so that the CPU is set in one of thenormal mode, the power-saving mode, and a sleep mode by controlling thepower supply unit, and, when the CPU is set in the sleep mode, a powerconsumption in the sleep mode is made to be smaller than a powerconsumption in the power-saving mode, the system control unit cancelsthe setting of the CPU is the sleep mode based on the control signaloutput by the comparator when the match occurs.
 12. The electricaldevice according to claim 11, wherein, when an error in the electricaldevice is detected before switching the CPU from the normal mode to thepower-saving mode, the system control unit inhibits the setting of theCPU in the power-saving mode.
 13. The electrical device according toclaim 11, wherein, after the CPU is set in the power-saving mode, thesystem control unit sets the return time into the register immediatelybefore setting the CPU in the sleep mode.
 14. The electrical deviceaccording to claim 13, wherein, after the CPU is set in the power-savingmode, the system control unit sets the return time in the sleep modewhen a temperature of an internal component of the electrical device isbelow a predetermined temperature.
 15. The electrical device accordingto claim 10 further comprising an image memory which stores image datareceived from an external device through the communication unit, whereinthe system control unit performs a facsimile reception by using theimage memory.
 16. The electrical device according to claims 15 furthercomprising a printing unit which prints image data on paper, wherein,when the CPU is set in the power-saving mode and an amount of the imagedata stored in the image memory exceeds a predetermined amount, thesystem control unit switches the CPU from the power-saving mode to thenormal mode and causes the printing unit to print the image data, readfrom the image memory, on paper so that the amount of the image datastored in the image memory is reduced.
 17. The electrical deviceaccording to claim 10, wherein the system control unit stores in thesystem memory a shift time that indicates a time the CPU is to beswitched from the normal mode to the power-saving mode, the systemcontrol unit storing in the system memory the return time that indicatesthe time the CPU is to be switched to the normal mode, and the systemcontrol unit switching the CPU to the power-saving mode when the shifttime is reached, and switching the CPU to the normal mode by causing theregister to output the control signal to the CPU when the return time isreached.
 18. The electrical device according to claim 10, wherein thesystem control unit further comprises a calculating unit calculating adifference between the current time of the clock and the return time ofthe register, and wherein the system control unit inhibits the settingof the CPU in the power-saving mode when the time difference calculatedby the calculating unit is not larger than a given period.
 19. A methodof controlling an electrical device having a communication unit, theelectrical device comprising: a system control unit controlling theentire electrical device, the system control unit having a CPU that isset in one of a normal mode and a power-saving mode by controlling apower supply unit, wherein, when the CPU is set in the normal mode, apower output from the power supply unit is supplied to electricalcomponents of the electrical device, and when the CPU is set in thepower-saving mode, the power supplied to the electrical components inthe normal mode is cut off or reduced and the electrical device is setin a standby state; a real-time clock keeping track of hours, minutesand seconds of a current time and outputting a signal indicating thecurrent time; a register; a comparator; and a system memory storing atleast one time-specified operation data, the method comprising the stepsof: setting a return time in the register, the return time indicating atime the CPU is to be switched from the power-saving mode to the normalmode; causing the comparator to compare the current time output from theclock with the return time stored in the register, and to output, when amatch occurs, a control signal to the CPU; reading, when thetime-specified operation data is stored in the system memory, atime-specified operation with an earliest transmission time from thesystem memory; setting the earliest transmission time into the registeras the return time; and switching the CPU to the normal mode when thecomparator outputs the control signal to the CPU so that the CPU isautomatically switched form the power-saving mode to the normal mode.20. The method according to claims 19 wherein the CPU is set in one ofthe normal mode, the power-saving mode, and a sleep mode by controllingthe power supply unit, and, when the CPU is set in the sleep mode, apower consumption in the sleep mode is made to be smaller than a powerconsumption in the power-saving mode, and the setting of the CPU in thesleep mode is canceled based on the control signal output by thecomparator when the match occurs.